A Solar System with an Earth-Size World, and a Planet in the Habitable Zone

Posted 22 April 2009 by Ian Musgrave

Image Credit ESO (click to embiggen). The Gliese 581 system delivers again. Giese 581 is a red dwarf star 20.4 light years away that until recently boasted the lightest extrasolar planet ever found. At 5 Earth masses, Gliese 581c was not exactly a second Earth, but it and 7 Earth mass Gliese 581d captured the worlds imagination as they seemed to be in the habitable zone of their parent star, where liquid water can exist. Now the smallest mass planet ever has been discovered around Gliese 581, a 1.9 mass planet Gliese 581e, presumably rocky, that screams around Gliese 581 in a little over three days. At a mere 0.03 Astronomical Units from its star, Gliese 581e is a Mercury-like world, baking in the close embrace of the Red Dwarf. Importantly, the orbit for Gliese 581d has been refined too. It is now definitely within the habitable zone of its star. Gliese 581d is likely very unlike Earth, and it and Gliese 581c are probably water worlds. The refinement of the orbit of 581d means it is very-likely covered in liquid water, when the planet was first described it seemed more likely it would be an ice world (but Gliese 581c is more likely to be Venus-like).

Unfortunately, even though Gliese 581 is so close that we can almost touch it, astronomically speaking, we won't be travelling there for a while. You can go there virtually though if you have the 3D space rending program Celestia, I have made an ssc file for the Gliese 581 system. If you have Celestia 1.5 and above, the program already comes with Gliese 591b, c and d (you will have to comment b and c out in my file, and comment out d in the extrasolar.ssc file as it has the old orbit). Download the file Wolf_562.ssc (the alternate name for Gliese 581) and put it in your Celestia extras folder and go exploring. For the original ESO press release go here. For a PDF of the discovery paper go here. And a Nature News commentary is here. Naturally the blogosphere has already caught on. Here's Stuart's take, Centauri Dreams, Dynamics of Cats, Starts with a Bang (and his update here), Science After Suneclipse on how long it would take to get to Gliese 581 and the Questionable Authority on what this means for finding alien civilizations (and how much you would weigh on Gliese 581d).

49 Comments

The Sanity Inspector · 22 April 2009

Wonder if there's any way of knowing if these planets rotate? I read somewhere once that planets in the "zone of habitability" around a red dwarf would be held in tidal lock, and bake on one side and freeze on the other.

Wheels · 22 April 2009

I've been looking for a reason to install Celestia again! The version in Hardy's repos is 1.5.0-1. That one has the old orbit?

fnxtr · 22 April 2009

The Sanity Inspector said: Wonder if there's any way of knowing if these planets rotate? I read somewhere once that planets in the "zone of habitability" around a red dwarf would be held in tidal lock, and bake on one side and freeze on the other.

Hmmm... a tidally locked water world... would the water boil away or would there just be magnificent storms and tides? Or a huge ice continent on the dark side? Given the suprising diversity of the Jovian and Saturnian satellites, there's really no guessing what these planets will look like.

fnxtr · 22 April 2009

Ian Musgrave · 22 April 2009

The Sanity Inspector said: Wonder if there's any way of knowing if these planets rotate? I read somewhere once that planets in the "zone of habitability" around a red dwarf would be held in tidal lock, and bake on one side and freeze on the other.

Currently, no. However, even with tidal lock there will be some libration, which means there will be some slight movement which will adjust temperatures in the twilight region. Also, the presence of an atmosphere will result in air mass circulation, cooling the "hot" side and warming the "cold" side. We see evidence for this sort of air circulation on the hot, tidally locked "super Jupiters". Also, current circulation in the water of a water world should moderate the temperature somewhat. fnxtr's vision of storms and tides, with a darkside ice continent might be a real possibility.

Ian Musgrave · 22 April 2009

Wheels said: I've been looking for a reason to install Celestia again!

You need a reason? That program is the ultimate is astro-cool! It already has a bunch of exoplanets, and you can add artificial satellites, new asteroids and comets (and even the two new Moons of Pluto when they came out). I use it to see where the STEREO spacecraft are pointing when I'm hunting for comets in STEREO spacecraft images.

The version in Hardy's repos is 1.5.0-1. That one has the old orbit?

Yes, that one has the old d orbit.

Vince · 22 April 2009

OT - But two more gaps to fill :)

See www.the-scientist.com/blog/display/55653/

veri kurtarma · 23 April 2009

When will we can see that planets clear photos? Are we still very far from that technology?

Peter Henderson · 23 April 2009

The Sanity Inspector said: Wonder if there's any way of knowing if these planets rotate? I read somewhere once that planets in the "zone of habitability" around a red dwarf would be held in tidal lock, and bake on one side and freeze on the other.

Yes, I think that's correct about the tidel lock sanity inspector. Also, don't forget that both Venus and Mars are in the habital zone around the sun and yet are so profoundly different from the Earth.

mrg · 23 April 2009

veri kurtarma said: When will we can see that planets clear photos? Are we still very far from that technology?

NASA is working on the Terrestrial Planet Finder: http://planetquest.jpl.nasa.gov/TPF/tpf_index.cfm No schedule, current work is on Webb Space Telescope. TPF may be a collaboration with the ESA. I doubt that even TPF will get much of an image, though -- extrasolar planet hunting is not just like trying to detect a firefly from the other side of the ocean, it's like trying to detect a firefly that's buzzing around a spotlight (there's this big bright star right next to it). "Tricky." MrG / http://www.vectorsite.net

lurker111 · 23 April 2009

Just as a matter of interest, where/what is Gliese 581a ???

eric · 23 April 2009

lurker111 said: Just as a matter of interest, where/what is Gliese 581a ???

"a" refers to the first planet in the Gliese 581 system (the one closest to the star), "b" refers to the second, and so on...

fnxtr · 23 April 2009

So what happens if they later find one closer to the star than 'a'? Out of sequence nomenclature like Saturn's rings, or do they rename them all?

amphiox · 23 April 2009

Actually, I think 'b' is used to refer to the first planet (discovered). Gliese 581a would refer to the star itself, but in common parlance most just use Gliese 581 and leave it at that.

amphiox · 23 April 2009

The planets are named in order of their discovery. Note that Gliese 581e, the newest one, is actually the closest one in (order is e, b, c, d). b was discovered first, c and d discovered at the same time, so c given to closer one in.

eric · 23 April 2009

amphiox said: The planets are named in order of their discovery. Note that Gliese 581e, the newest one, is actually the closest one in (order is e, b, c, d). b was discovered first, c and d discovered at the same time, so c given to closer one in.

Amphiox thanks for correcting my mistake. Which I shouldn't have made, considering I only had to click on the figure to see what was going on... ah well, the price of laziness...

Ineffable · 23 April 2009

It seems as if scientists are confirming the scientific hypothesises put for by Gonzalez and Richards in cosmological ID about the habitable zone and discoverability. Perhaps the posters at PT will retract their statement about Gonzalez's ID research being "vacuous" now. (I won't hold my breath though

fnxtr · 23 April 2009

... this should be good....

James F · 23 April 2009

Ineffable said: It seems as if scientists are confirming the scientific hypothesises put for by Gonzalez and Richards in cosmological ID about the habitable zone and discoverability. Perhaps the posters at PT will retract their statement about Gonzalez's ID research being "vacuous" now. (I won't hold my breath though

Of course not, we're the Global Darwinist Conspiracy™! We demand things like evidence and testable mechanisms regarding an "intelligent agency!"

Who controls the British Crown?

Who keeps the metric system down?

We do, we do…

Who keeps Atlantis off the maps?

Who keeps the Martians under wraps?

We do, we do…

Who holds back the electric car?

Who makes Steve Gutenberg…a star?

We do, we do…

Who robs cavefish of their sight?

Who rigs every Oscar night?

We do….We doooo!

mrg · 23 April 2009

fnxtr said: ... this should be good....

I was thinking exactly the same thing. But I'm just going to lurk and watch. MrG http://www.vectorsite.net

raven · 23 April 2009

It seems as if scientists are confirming the scientific hypothesises put for by Gonzalez and Richards in cosmological ID about the habitable zone and discoverability. Perhaps the posters at PT will retract their statement about Gonzalez’s ID research being “vacuous” now. (I won’t hold my breath though

Um, no. The concept of habitable zones around stars was developed decades before Gonzalez was even born. Discoverability just means we have eyes, brains, and science. Gonzalez might have figured that out by himself but it was known millenia ago. Your simple minded fallacies of Appeal to Authority are bad enough but you have gone further and it is now Appeals to Dimwitted Crackpots. PT and others dealt with the book years ago and it has sank without a trace in the scientific community.

Preface Why ID Fails: Matt Young and Taner Edis: The recent book The Privileged Planet, written by astronomer Guillermo Gonzalez and theologian Jay Richards, argued that our Earth is almost uniquely situated in the universe to allow for intelligent life and to give that life the best possible opportunity to observe and learn about the universe. The authors, however, are evidently more concerned about winning over the general public than the scientific community: The Privileged Planet was soon accompanied by an attractively produced video with the same title, suitable for showing to a TV audience who would have been unable to distinguish it from a credible science documentary. The Discovery Institute arranged for a showing at the Smithsonian Institution, only to be turned down later because of outrage among mainstream scientists. Politically, ID could not lose: If the film was shown at the Smithsonian, it could be presented as an acknowledgment of ID by a prestigious scientific institution. But when official cosponsorship was withdrawn due to such concerns, ID advocates insisted that the affair was yet another example of suppression of debate by the Darwinian orthodoxy. The Privileged Planet, however, offers little that is fundamentally different from the widely criticized argument that physics has been fine-tuned by a creator specifically to produce intelligent life. It would have been notable as only another attempt to press some curious astronomical facts into the service of a classic flawed argument––if not for the political strength of ID creationism.

raven · 23 April 2009

If anything, the discovery of common planets around stars undermines Gonzalez's theory. We are limited right now by the power of our instruments and already a common star like Wolf/Gliese has been found to have 5 planets at a minimum, probably more.

The theory of solar system formation and our observations make it likely that most stars have solar systems.

Gonzalez's book was just Anthropic Principle meets GODDIDIT, a rehash of old material without anything new.

There are some theories that red dwarves like Gliese might be ideal for habitability. They are the most common stars in the galaxy, orders of magnitude more common than our G class sun. They also last longer by up to a thousand fold.

Our biosphere is living on borrowed time. In a billion years or so, the sun will be much hotter and we will fry.

Our galaxy isn't looking so great either. In two billion years it will collide with Andromeda, in about the largest collision at this stage of the universe. Galaxies collide all the time and ours is colliding with several right now. These are all dwarf galaxies, maybe 1/100 or less the size of ours.

Two large spiral galaxies colliding is the difference between a car running into a bunny and a car running into another car. What will happen is unclear but could well make both galaxies rather unfriendly for life. This may also be one of the last or even the last time two big spirals collide. The universe is expanding and due to dark energy this expansion is increasing in rate.

A better book than Gonazalez's would be Doomed Planet in a Doomed Galaxy.

Stanton · 23 April 2009

Ineffable said: It seems as if scientists are confirming the scientific hypothesises put for by Gonzalez and Richards in cosmological ID about the habitable zone and discoverability. Perhaps the posters at PT will retract their statement about Gonzalez's ID research being "vacuous" now. (I won't hold my breath though

Please tell us what research papers Gonzalez has written for "cosmological Intelligent Design and the habitable zone and discoverability." Also, please show us specifically how Gonzalez's research is helping astronomers find Earth-like planets.

Flint · 23 April 2009

I may not remember this completely, but I thought Gonzalez was one of those who proposed that there is a galactic habitable zone, as well as a stellar zone, for (water-based) life as we know it. And that there is some cogent argument (that is, based on evidence) as to why this might be so.

But while Gonzalez may have been tangentially involved in this research, this by no means supports or demonstrates any "ID research". If anything, ID is simply (and artificially) plastered on after the fact. One might as well argue that "ID" is supported by the observation that (1) water tends to run downhill and concentrate in valleys; and (2) People tend to settle where water is available, and so water was intelligently designed to run downhill.

In other words, research identifying galactic zones humans would find habitable is valuable. Claiming that "therefore goddidit" is empty and vacuous.

Mike Elzinga · 23 April 2009

Flint said: I may not remember this completely, but I thought Gonzalez was one of those who proposed that there is a galactic habitable zone, as well as a stellar zone, for (water-based) life as we know it. And that there is some cogent argument (that is, based on evidence) as to why this might be so.

This claim that Gonzalez is the originator of “habitable zones” or “stellar zones” is something that actually astounds me. These ideas are really old. I remember as a kid back in the 1940s and 50s reading about these concepts in popular magazines such as Popular Science, Scientific American, and others. And in those magazines, these ideas were attributed to cosmologists and scientists going back into the 19th century and probably much earlier. They are certainly obvious to anyone speculating on the conditions necessary for life as we know it. When and where did the attribution of these concepts to Gonzalez occur? My impression has been that these are excessive claims by the ID/creationists to pump up the credentials of the newly minted PhDs in their midst.

fnxtr · 24 April 2009

Whoa! I've been playing with Celestia all day. Douglas Adams would have loved it. Total Perspective Vortex, indeed. It's so easy to get lost....

mharri · 24 April 2009

Ineffable: Wait -- what? How again does finding exoplanets which are even more like Earth support the idea of a privileged planet?

I'm not joking. I would like a sense of how this line of reasoning works. (And please, guys, no snarky comments.)

stevaroni · 24 April 2009

I would like a sense of how this line of reasoning works.

It doesn't. It's the Johnny Cochran Defense. If you have no real argument, muddy the waters.

fnxtr · 24 April 2009

It may support the idea of a galactic habitable zone, which in itself is zero support for PP. Basically Gonzalez et al seem to be saying we're special because we're right in this particular area of the galaxy with only a few billion other stars... typical pretzel logic.

HDX · 24 April 2009

Actually it is the 'Chewbacca defense' but comes from Johnnie Cochran's character on South Park.

stevaroni said:
I would like a sense of how this line of reasoning works.
It doesn't. It's the Johnny Cochran Defense. If you have no real argument, muddy the waters.

Mike Elzinga · 24 April 2009

fnxtr said: It may support the idea of a galactic habitable zone, which in itself is zero support for PP. Basically Gonzalez et al seem to be saying we're special because we're right in this particular area of the galaxy with only a few billion other stars... typical pretzel logic.

It’s basically another manifestation of the “Lottery Winner Fallacy”; conflating “X wins the lottery” with “someone wins the lottery”. They do this a lot.

Wheels · 24 April 2009

stevaroni said: It's the Johnny Cochran Defense. If you have no real argument, muddy the waters.

Isn't that what defense attorneys are SUPPOSED to do, though?

James F · 24 April 2009

Mike Elzinga said:
fnxtr said: It may support the idea of a galactic habitable zone, which in itself is zero support for PP. Basically Gonzalez et al seem to be saying we're special because we're right in this particular area of the galaxy with only a few billion other stars... typical pretzel logic.
It’s basically another manifestation of the “Lottery Winner Fallacy”; conflating “X wins the lottery” with “someone wins the lottery”. They do this a lot.

Yet, they are so quick to claim that "odds" against a specific mutation in a protein sequence occurring are too high. I guess creationism means never having to be consistent.

Flint · 24 April 2009

These ideas are really old. I remember as a kid back in the 1940s and 50s reading about these concepts in popular magazines such as Popular Science, Scientific American, and others. And in those magazines, these ideas were attributed to cosmologists and scientists going back into the 19th century and probably much earlier. They are certainly obvious to anyone speculating on the conditions necessary for life as we know it.

Yet, I distinctly remember reading sometime in the last decade at the most, that the notion of a galactic habitable zone is new. Yes, a stellar zone is a very old idea - water must be liquid. But the galactic zone had nothing to do with water, and a lot to do with ambient radiation and other phenomena (can't remember anymore). And these things were NOT obvious, which is why Scientific American devoted a long article to them recently. Even today, science fiction authors current in their science tend to postulate dense populations of intelligent aliens in the galactic core cluster of stars, simply because there are so many stars there. I have no idea whether Gonzales has been involved in the development of this model.

Mike Elzinga · 24 April 2009

James F said: Yet, they are so quick to claim that "odds" against a specific mutation in a protein sequence occurring are too high. I guess creationism means never having to be consistent.

Right. I think this is also the same fallacy. Once a particular mutation occurs, it becomes “special” to them. However, a different mutation might produce something different. Why then is that not also special? Basically the ID/creationists are assuming what is is the same as what must be. But simply glancing back over evolutionary history and at the vast numbers of living organisms currently in existence shows that lots of things fall out of the contingencies of history. Change the contingencies even slightly, and other things fall out.

Mike Elzinga · 24 April 2009

Flint said: Yes, a stellar zone is a very old idea - water must be liquid. But the galactic zone had nothing to do with water, and a lot to do with ambient radiation and other phenomena (can't remember anymore). And these things were NOT obvious, which is why Scientific American devoted a long article to them recently. Even today, science fiction authors current in their science tend to postulate dense populations of intelligent aliens in the galactic core cluster of stars, simply because there are so many stars there. I have no idea whether Gonzales has been involved in the development of this model.

Well, now you got me wondering. I’ll have to do more checking. My recollection would place these ideas certainly back more than 40 or 50 years ago. I was certainly aware of radiation hardening of space probes back then. Gonzalez would have been too young. But then, at my age, anyone younger than 50 is a kid. Who knows what I have forgotten?

eric · 24 April 2009

fnxtr said: It may support the idea of a galactic habitable zone, which in itself is zero support for PP. Basically Gonzalez et al seem to be saying we're special because we're right in this particular area of the galaxy with only a few billion other stars... typical pretzel logic.

I'm going to write a book called "Privileged Vent." It will take PP to its logical conclusion: if our planet's specialness is a sign of design, then the extra special uniqueness of the deep sea vent ecology on our planet must mean that the entire universe was designed for vent-dwellers. Hey I could do a whole series of these. If the uniqueness of the vent ecology is a sign of design, then in book 2 I could choose one specific vent and talk about how the universe was designed for it. In book 3 I could talk about how the special uniqueness of one particular face of that vent means the universe was created for it, book 4 could be about a few square centimeters on that face, then...

raven · 24 April 2009

One of the many flaws in Gonzalez's book is his sample size. There are 200 billion-1 trillion stars in our galaxy. And who knows how many galaxies.

He is drawing sweeping conclusions based on a sample size of...1 solar system, not well studied on the ground.

We need a lot more data here.

mharri · 24 April 2009

That's what I was thinking, though I thought I might get a better sense of the disconnect if I could get the original speaker to explain slowly and methodically the reasoning; granted, many visitors of such an outlook have a weird habit of being one-post wonders. Oh, well. I picked up "galactic habitable zone" as websearch fuel; and that is still a learning opportunity.

eric · 24 April 2009

Question for the astronomers out there. If you were sitting 20 light years away and had the same telecscopes used to look at Gliese pointed at our system, what would you see? Jupiter? Jupiter, Saturn, and Uranus? None of them? All of them plus the rocky planets?

Reed · 25 April 2009

eric said: Question for the astronomers out there. If you were sitting 20 light years away and had the same telecscopes used to look at Gliese pointed at our system, what would you see? Jupiter? Jupiter, Saturn, and Uranus? None of them? All of them plus the rocky planets?

Not an astronomer, but an interested amateur. You wouldn't see any of them, just as we do not see the planets of the Gliese 581 system. The planets in this system were detected by radial velocity measurements. You might find this blog post (and the paper linked from it) to be of interest. AFAIK we wouldn't be able to detect a sol-like system by radial velocity methods using current instruments. The planets are too far away given the masses involved. The Gliese 581 is easier because the mass of the star is much smaller, the orbital periods of the planets much shorter, and the masses of the planets are relatively high. The recently launched Kepler mission should be able to detect transits of earth sized planets, but this requires the planet be aligned exactly right to pass between us and the star. Keep in mind also that you need to observe multiple orbits to confirm a planet with either of these methods. To detect the earth (never mind the outer planets) you'd have to observe for several years.

Ian Musgrave · 26 April 2009

eric said: Question for the astronomers out there. If you were sitting 20 light years away and had the same telecscopes used to look at Gliese pointed at our system, what would you see? Jupiter? Jupiter, Saturn, and Uranus? None of them? All of them plus the rocky planets?

As Reed said, none of them. Our worlds are too close to the Sun to be picked up by normal telesscopes. The radial velocity measurements used to pick up these worlds wouldn't work in our solar system as the rocky worlds are too small, and Jupiter too far away, to pick up with current measurement systems (we would have to wait 12 years, the time it takes for Jupiter to orbit the Sun once to be able to detect any wobble, and you would normally wait a number of years to be sure of the detection).

Torbjörn Larsson, OM · 27 April 2009

I almost feel guilty for commenting here, seeing that I promised to discuss abiogenesis with eric I believe. But I have been, and will be, short on time so I have to make short snippets (and use them for necessary breaks. ;-) So I'll start here. Oh, and Reed, thanks for the reference on astrobiology review.

There are 200 billion-1 trillion stars in our galaxy.

A fairly recent and thorough paper on the GHZ that got my attention, for its nice graphs if not else, is Lineweaver et al in Science [2004]. I haven't had time to really read it, but a scan suggests they look at metallicity and SNe constraints over time. For possibility of complex life (i.e. here: terrestrial planets older than 4 Gy) they find "The 68% contour contains less than ~ 10% of the stars ever formed in the Milky Way." Most of those stars (~ 75 %) are currently ~ 1 Gy older than Earth. The number of stars that contain recent life is currently ~ 30 % and increasing with the increased size over time of the GHZ. The average of all stars that could have life is currently ~ 1 Gy younger than Earth. IIRC, recent observations is that terrestrial planets may be at least as likely around low metallicity stars for some reason (perhaps tied to the possibility for super-Jupiters), probably inconsistent with the paper's model, so the GHZ may be a lot larger than 20 - 100 billion stars. Btw, since the GHZ still is a numbers game in the absence of tests, and IDiots like those, I also note that Lineweaver is the same guy who has a paper that puts a lower limit on the possibility for life on habitable planets from the observed speed that it occurred here on Earth against a model of repeated abiogenesis attempts and extinctions. IIRC, at least ~ 16 % of habitable planets should have life to be reasonably consistent with that single observation, possibly many more. The odds quickly stack up these days that we aren't alone out there.

Torbjörn Larsson, OM · 27 April 2009

"The number of stars that contain recent life" - that aren't excluded from containing life

fnxtr · 27 April 2009

If we are not a miracle, and the nature of matter is consistent throughout the galaxy, then life elsewhere is pretty much inevitable. Given the time and distance we have to work with, though, finding it will be pretty much impossible. Or at least highly improbable.

Henry J · 27 April 2009

And, if we are a miracle (whatever that word even means), the odds couldn't be computed from basic principles. (Miracles might or might not be unique, at the whim of the one responsible.)

Henry

fnxtr · 27 April 2009

Quite so.

elite jackson · 16 December 2009

no planet to on the Image this website is not the another Earth plant

D. P. Robin · 16 December 2009

elite jackson said: no planet to on the Image this website is not the another Earth plant

I think there was an English sentence in there at the start, but it is hard to find it now. dpr